NEC: National Electrical Code (U.S.)

negative pressure: Condition that exists when less air is supplied to a space than is exhausted from the space, so the air pressure within that space is less than that in surrounding areas.

NFPA: National Fire Protection Association

NIOSH: National Institute for Occupational Safety and Health.

non-combustible: a substance that will not burn when subjected to fire.

normal operating controls: devices, such as thermostats, that would be operated by ordinary occupants which require no specialized skill or knowledge.

NTIS: National Technical Information Service.